Acquired marine seismic data (and some other forms of collected data) typically contains source and receiver “ghost”, which refers to energy introduced due to spurious reflections from a relatively strong reflecting interface, which in the case of acquired marine seismic data may be the free sea surface. The ghost limits the temporal resolution of the seismic wavelet, controls the roll-off of the data spectrum at low frequencies and introduces spectral notches at higher frequencies. Constructive and destructive interferences of the ghost events with the up-going wavefield introduce frequency and propagation angle dependent perturbations. Source and receiver cable depths and the dimensionality of the wavefield directly impact the ghosts; and in practice, other factors, such as acquisition noise, weather expectations and acquisition/processing capability affect the process of removing the ghosts.
Traditionally, a process to remove ghost, called “deghosting,” is applied on pre-stack data and at a relatively early stage in the processing chain so that subsequent pre-migration processing takes advantage of a sharper wavelet (e.g., velocity analysis and so forth).